Cardiovascular exercise has many benefits, including increased fat loss and a healthier heart. Though cardiovascular exercise should have a place in any exercise regimen, cardio in excess of two to three hours a week can lead to problems because of increased production of cortisol. These problems include decreased fat metabolism and a weakened immune system.

What is Cortisol?

Cortisol is a hormone produced by the human body to deal with stress. It is secreted by the adrenal glands to signal to the rest of body that energy must be conserved. Skeletal muscle is the most inefficient tissue in the body when it comes to energy storage. Consequently, cortisol will cause the stressed body to turn on its muscle stores as its first possible source of energy. Fat, on the other hand, is the most energy efficient tissue in the body. As such, cortisol slows down your thyroid to conserve fat stores. Those who are trying to lose fat should aim to keep cortisol levels as low as possible since high levels of this hormone could inhibit their progress significantly.

Does Cardio Significantly Raise Cortisol?

It's easy to point the finger and say that cardio should be avoided, but science demonstrates that the truth is a bit more complicated. One team of scientists found evidence that moderate cardiovascular exercise could actually lower cortisol levels. Yet, the human body adapts to cardio easily, and will require longer durations performed at higher intensities to continue burning fat after several weeks of performing cardio at moderate levels. Consequently, even lower intensity cardio could Indirectly lead to increased cortisol production because you will eventually need to move to higher intensity levels for longer durations.

How to Avoid Raising your Cortisol

You can avoid raising your cortisol levels by keeping the length of your cardio sessions under 45 minutes, performing under five sessions a week, and varying the type and intensity of the cardio that you perform. These measures will ensure a happy medium where you keep your body from adapting to the cardio while keeping the stress on your body low enough to keep cortisol levels down.

Seeing the Signs

Know the signs that your cortisol levels are high. If you get the chills or feel like you have a cold that won't go away, chances are your cortisol levels are high. Stop doing cardio for a few days, take a rest and raise your calories. You'll feel much better after you've had a few days to rest, and the reduced stress should also reduce your cortisol.

Conclusion

Cardiovascular training is an important tool in any fitness program. Nevertheless, doing too much of the same types of cardio could lead to increased production of cortisol and sabotage your progress. Increase the variety of your workouts, vary the intensity and watch your results progress.

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About the Author

Christopher Albert is the co-owner of a gym in Long Beach, Calif., where he also serve as head body composition specialist. He is a certified personal trainer with the National Academy of Sports Medicine and holds an M.A. in international relations from the University of Connecticut.